Solenoid Actuators
Turbo Mini Forums

I belive RC stepper motors have an op amp in and feed back a voltage into one of the op amp inputs.

http://images.google.co.uk/imgres?imgurl=h...DN%26start%3D20

I was thinking that I could use a hacked RC servo to control my vanes with positional feedback, controlled form a pressure transducer, then have a switch with several positions to change the voltage reference to give diferent boost settings.

This I can understand:



Just need a logic circuit to drive the inputs.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

a 10 psi actuator starts to crack open at 10 psi :)

the force on the wastegate flap, assuming a small restrictive turbo is used, will cause boost to drop towards teh top of the rev range as the airflow through the gate and the pressure it exerts becomes greter than the wastegate spring. if the boost is then controlled by a bleeding device this effect becomes greater still.

A practical example: on a skyline gts-t a very wide diameter diafram wastegate is used, this meens even though the gate only opens at around 8psi, the spring pressure is huge. the engine holds 8psi to the red line. substitute this actuator for a smaller conventionaly sized actuator that opens at the same pressure (therefore weaker spring) and the boost tails off up the top of the rev range.

in theory (imho ofcourse) if you use a servo you rule out the force of exhaust gases on teh wastegate flapper, and as your only source for closed loop controll becomes manifold pressure you will have much much more stable boost, assuming the closed loop controll functions correctly.

im implying the use of a worm driver servo, not a stepper btw, as this should be imune to any forces from the driven end. to a point atleast.

EDIT: stupid mistakes :)

Edited by evolotion on 19th Feb, 2010.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

This is the problem we had on the RR. The actuator would not hold more than 15psi, even totally disconnected from the MAP. Which is what got me thinking. A new, better quality, actuator will probably sort it.

But a proper PID controller would be much better.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

I can't find any deifinative circuits on the web about how to control the above stepper motor circuit.

However, it looks like we can use a voltage comparator Op Amp to achieve the step output and then another to determine the direction. Possibly also a counter to keep it stepping.

But then I'm guessing.

I think PID wuld be a little too elaborate and require programmable kit.

Edited by Paul S on 19th Feb, 2010.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I think you can do PID on a pic so it would not be silly. Mind you I think I need to get my car working before I start doing nice and innovative things.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."